Paint spray machine



June l5, 1943. Y T, F; B'RACKETT l 21,321,982

PAINT SPRAY MACHINE Filed Jan. 2, 1941 6 Sheets-Sheet 1 :inventor June l5, 1943. T. F. BRACKETT PAINT SPRAY MACHINE Filed Jan. 2, 1941 6 Sheets-Sheet 2 v Gttorneg June l5, 1943. fr, F. BRACKET'T PAINT SPRAY MACHINE Filed Jan. V2, 1941 6 Sheets-Sheet 3 By ww 9- EZ' Gttomegs June 15, 1943-. T. F. BRACKETT 2,321,982

. PAINT SPRAY MACHINE v Filed Jan. 2, 1941 v e sheets-sheet 4 '..nll Snventor June 15, 1943.

T. F. BRACKETT PAINT SPRAY MACHINE 6 Sheets-Sheet 5 Filed Jan. 2, 1941 Jun111,1943.V T, F BRACKETT 2,321,982

11.1111 SPRAY MACHINE Filed Jan. 2; 1941v 6 Sheets-Sheet 6 Snnentor Patented `lune l5, 1943 f l.2,321,982l

PAINT SPRAY MACHINE Tracy F. Brackett,.Detrolt, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application January 2, 1941, Serial No. 372,754

s clams.

This invention relates to the finishing oi.' surfaces and more particularly to an improved paint spraying apparatus. production of automobile bodies, the apparatus is designed for association with the usual conveyor system which carries bodies successively along a line of work performing stations, and to operate as automatic equipment for painting the top and both side walls of bodies presented to it in the continuous travel of the conveyor.

In current streamline styling of automobile bodies the wall surfaces are curved in all directions, both longitudinally and transversely, with an intermediate bulge so that the contour from the front or leading edge rises and then recedes toward the rear or trailing edge, the rearward slope being most pronounced. For uniform coating it is important to maintain a given spray distance between the surface and the gun nozzle and to keep the gun aimed in a direction substantially normal to the surface. Accordingly it is one of the objects of the present invention to provide mechanism operating automatically to shift gun position for following the changing surface contour presented by body travel whereby both gun aim and spray distance are held within practical limits. y

In a preferred embodiment of the invention, the factory conveyor car-ries bodies successively at a given rate through the paint station or' spray zone wherein are located adjustable side and top gun tracks extending transversely to the direction of body travel'and having guide contours conforming substantially to the transverse curvature of the body. Reciprocating gun carriages ride on these tracks and as the spray guns traverse the roof and side wall surfaces their spray distance and aim with respect to transverse body curvature are controlled by track curvature. With respect to longitudinal body curvature, gun spray. distance and aim are controlled by bodily shifting the gun tracks and the adjustment of the tracks for this purpose consists of provision for their translatory movement in and out in relation to direction of conveyor travel as well as a swivel movement, respectively, about an axis parallel to the'y direction of gun reciprooation. Thus in the case of a body having an intermediate bulge in the longitudinal direction the movement of the tracks will be outward as the body pro- As employed in the factory gresses through the spray zone from the leading edge to the high point of the bulge and then willrected rearwardly or toward the oncoming body at the start to positions in which the guns at the end of the spraying operation are directed forwardly in the direction of body travel. The net result. therefore, is that the nozzles of the reciprocating spray guns follow paths conforming to both longitudinal and transverse curvatures and are at all times properly spaced from and directed at the surface presented within their spraying range.

For a more complete explanation reference will be made to the accompanying drawings wherein Figure 1 is a front elevation of the complete spray mechanism; Figure 2 ls a plan view of the lower portion `of the apparatus, with parts in section, as on line 2-2 of Figure 1; Figure 3 is an enlarged detail view of a part of the operating mechanism for gun travel on one side; Figure 4 is a; front elevation of a portion of the mechanism as viewed on line 4-.4 of Figure 2; Figure 5 is a side elevation of the machinev looking in the direction of the arrows on line 5 5 of Figure 2; Figure 6 is a vertical section showing the driving mechanism for the roof spraying gun and is taken on line 6 6 of Figure 1; Figure 7 is an enlarged detail View taken on line i-l of Figure 1; Figure 8 is an enlarged view showing a fragment of the machine at one end of the top track; Figure 9 is an end view looking in the direction of the arrows on line 9-9 of Figure 11 and showing a part of the track control mechanism and the 'control devices for varying the character of track adjustment, and Figures l0 and 11 are sectional views taken on lines llil0 and ll-ll', respectively of Figure 9.

The conventional conveyor system as used in the body plant includes a continuously moving chain indicated in the drawings by the numeral I to which are secured by tow bars in predetermined spaced relation, the body carrying dollies or trucks 2. Each truck carries a body and moves it through the several work performing stations. The outline of a body 3 ls illustrated in the drawings and indicates the transverse curvature in the top and side walls. It will' be understood, of course, that in the longitudinal direction the body walls are als..curved.

For applying the paint to the curved side walls there are provided spraying mechanisms on opposlte sides of the path of body movement.' In each instance the spraying mechanism includes a set of two spray guns 4-4 arranged for reciprocation in a vertical plane across the area to be covered. Flexible 'hoses or conduits accommodate the movement of the guns and as seen in Figure 1 these hoses for each gun are three in number, one intended to carry the supply of paint, the second to carry air under pressure for delivering an atomized spray of paint at the discharge nozzle of the gun and the third hose carrying a column of air for opening and closing the valve of the gun. Each side wall painting gun is mounted on a carriage 5 which as best seen in Figure 5 may consist of a pair of spaced plates having between them a series of three guide rollers 6 for running engagement on the opposite edges of a. vertically extending track 1. The guide edges of the track are curved so as to define a path of gun reciprocation in substantial conformity to the curvature of the side wall traversed by the gun.

Reciprocation of both carriages is effected through common driving means and to obtain counterbalance the carriages are arranged so that one runs up as the other runs down and this offset arrangement also provides an overlap in the y surface areas covered by the respective guns.

The gun reciprocating mechanism includes a series of endless chains 8-8 arranged in two sets and running over upper and lower sprockets 9 and I8. Motion of the chain is imparted to the gun carriages through connecting links II joining each carriage to an adjacent chain assembly. The uppermost set of sprockets 9 are mounted on a common shaft having a bearing in the upright frame structure I2 which also ties together the.

upper ends of the two side tracks 1-1. The frame assembly also provides a bearing for the shaft on which the lower sprockets I8 are mounted and as best seen in -Figure 3 the sprocket shaft at an intermediate point carries a drive sprocket I3 engaged by drive chain I4 which in turn is driven from a gear reduction box I5 mounted on the base or platform I6 from which the gun tracks 1-1 project upwardly. The gear reduction box driving-mechanism is coupled through a split pulley and variable speed drive belt assembly I1 from an electric motor I8. For varying the speed of gun reciprocation to fit the speed of conveyor travel, the distance between pulley centers may be changed by adjustment of a hand wheel I9 for operating the jack screw 28 mounted on the upright frame and engaged by threaded brackets which carry the electric motor I8.

The base or platform supporting the gun side tracks includes a pair of spaced transversely extending rails of channel or I section which are mounted for in and out adjustment to control spray distance, on spaced wheels or rollers 2| carried by a swinging sub-base assembly 22. This sub-base assembly 22 is located for swinging adjustment by a, pivot bolt or pin 23 whose axis extends vertically or in the general direction of gun reciprocation. At its outer end the sub-base 22 is supported by a pair of rollers 24 arranged on axes radially related to the pivot pin 23 and which are arranged to roll on bearing plates 25. The swiveling adjustment of the sub-base 22 rocks the side tracks so as to direct the spray gun nozzles in directions substantially normal to the body surface at any point of longitudinal curvature.

The roof traversing gun 26 is suspended 'on the reciprocating carriage 21 which like the side gun carriages previously described, includes a pair of spaced plates, and as best seen in Figure '1, a series or rollers 28 located between the plates and arranged to ride on the opposite edges of a roof track 29. The contour of the roof track is selected to direct the gun substantially normal to the roof surface at any given point and, t9 @Barry the gun in a path which substantially conforms to transverse roof curvature.

To cushion inertia forces and assist the carriage to reverse its direction of movement at opposite limits of its range of reciprocation, motion checking devices are provided each in the form of a dash pot; structure. best shown in the enlarged View in Figure 8. Each device includes a fixed cylinder 38 and a sliding piston 3l having a rubber bumper or nose 32 adapted to be engaged by an outwardly projecting abutment 33 on the gun carriage. The stem of the piston projects through a restricted sleeve 34 in the bottom of the air cylinder 38 and the opening through the sleeve communicates the air cylinder with an air storage chamber 35 which may be connected by a flexible hose 36 to a source of air under pressure. The supply of air under pressure tends to project the piston and the compression of the air upon inward movement of the piston cushions the force of carriage travel at the point of reversal of direction.

For imparting reciprocatory travel to the carriage a connecting link 31 is universally joined at opposite ends to the carriage 21 and to a.'

reciprocating slider 38. The slider 38 rides on a straight track 39 carried by the frame of the machine and is joined to a pair of flexible steel cables 48 which run over pulleys 4I, 42. 43, 44 and 45,*all carried by the frame of the machine, with the last mentioned pulley being mounted on a swinging lever 46 whose lower end is joined to a cable tensioning rod and coil spring assembly 41. To one of the vertical reaches of the cables 48 is fastened a slider 48 having rollers running between guide tracks 49. The slider 48, as best seen in Figure 6, is joined by a connecting rod 58 to an endless chain 5I which runs on upper and lower sprockets 52 and 53. The shaft of the uppermost sprocket 52 carries a belt driven pulley 54 driven through a gear reduction box 55 drive coupled by a belt 56 to a driving motor 51. j

The frame for supporting the roof track includes a pair of uprights 58 on both sides of the conveyor line and a cross connecting bar 59. Immediately below the rigid bar 59 is a vertically adjustable and rockable tube 68 having its ends projected-between and guided by the spaced i frame members or uprights 58-58. This tube 68 has its ends supported in rollers 6I-6I 4carried in a triangular plate 62 which is pivoted to an arm 63 fixed to a rockshaft 64 extending from side to side of the assembly and being pivotally mounted in brackets 65 carried by the adjacent upright 58. As seen in Figure 5 a dependent rod 66 on each arm 63 has a fixed abutment to engage the upper end of a coil spring 61 supported by the frame to carry yieldably a part of the load imposed on the crank arms 63. Near each end the vertically adjustable rock bar 68 has secured thereto a diamond shaped plate 68 whichprovides rigid lever arms projecting on opposite 'sides thereof and each of which carries a suspension. link 69 coupled to the corresponding arm of another diamond shaped plate or lever 18 to which is fastened an adjacent end of the roof track 29 so as to provide a parallelogram linkage which locates the track 29 and causes it to follow the movement of the adjustable rail 68.

At one end only of the adjustable tube 68 is a third diamond shaped plate 68' whose lever arms are coupled to the upper ends of a pair of push rods 1I-1I whose lower ends are joined to a pair of motion modifying levers 12-12 pivotally mounted in a support bar 13 carried by the frame uprights 58. Each motion multiplying link 12 in turn is pivotally joined tothe upper end of a push rod 14-14 whose lower end runs between guide rollers 15 and carries a camfollower roll 16. Rotating cams 11 engage the followers 18 and cause the push rods to be moved up and down in predetermined combinations as provided for in the contours of the associated cams.11-11 whereby to vary the vertical and tilted position of the roof spray gun as called for by longitudinal roof curvature.

The roof track control cams 11--11 are mount'- ed for rotation through shafts carried in a pair of transversely spaced bars 18 at the bottom of the upright framing members 58 and are geared together by a drive -fchain 19. At its inner end the driving shaft, as best seen in Figure 2,'carries a rotating cam 80 to engage a crank arm 8| on a transverse rockshaft 82 extending under the conveyor track and having at each end a crank army 83 joined by a link 84 to an adjacent sub-base of a side track assembly. Upon rocking adiustment of the shaft 82 the two sub-bases and gun track assemblies on opposite sides of the conveyor are rocked about their respective swivel connections 23 for directing the guns toward the body surface as before described.

At its end opposite the control cam 80 the driving shaft carries a pair of cooperating cams 85 and 86 (see Figures 9 and 11), the latter of which engages a follower roll on a swinging lever l81 which is pivotally mounted on'a pin 88'at its lower end and which carries on a pivotal mounting at its upper end, a second lever member 89 having a follower roll for engaging with the cam 85. Formed on the front face of the lever 89 by spaced guides-80 is a vertical groove or keyway in which is slidable a bearing block 9|. 'I'his sliding block has a horizontally projecting pin on which is pivoted a connector head 92 having pivotal connection on a vertical axis with one end of a connecting rod 93. The opposite end of the connecting rod 93 is`universally jointed to a rock lever 94 on a vertical shaft 95. On its lower end the rockshaft 95 carries a lever 96 which is joined by a connecting link 91 v(see Figure 2) to the sliding base of the nearest side track assembly and is joined by a link 98 .to one arm of a bell crank or motion reversing lever 99.

The other arm of the bell crank 99 is connected 'f by a link |00 to the sliding base of the other side trackassembly sov that the two sets of side tracks are moved in unison toward and away from one another in accordance with the changing width of the body presented in the spraying zone.4 A

tension spring |0|l may be arranged to exert its force on the bell crank 99 to maintain cam followers on the levers 81 and 89 'against their respective driving cams. .A

The character of the movement imparted through the linkage may be modified by changing the effective leverage of the parts through adjustment of the slider 9 I. For this purpose the slider is connected by a rod to a slidable piston |02 acting within an air pressure cylinder |03 and against the tension of a piston/retreating spring contour of the body presented in the spraying zone is preferably made dependent upon travel of the body through the zone. For this purpose the driving shaft oi the control mechanism is coupled through a train of chains and shafts, all indicated for simplicity bythe reference numeral |04, with a drive chain |05 extending beside the conveyor chain and having a length somewhat in excess of the length of the body conveying truck 2 as best seen in Figure 2. 'I'he endless driving chain |05 may be provided with a seriesof spaced upstanding arms, any one of which will be engaged by the forwardly moving truck 2 and carried with it during the continuous travel'of the conveyor.

The control of the spraying action of the sev- 'eral guns andv their driving motors may be effected through suitable valves and switches arranged for manipulation manually by the machine attendant or automatically in timed sequence through cycles determined by the character of the bodies and 'their spaced succession. Optionally machine action m'ay be dependent upon travel of a body 4through the region of the spray zone, as for example, through the use of' one or more electric eye devices arranged for interruption of protected 1 light incident to body travel.

I claim:

1. In a machine for painting the side walls of a traveling body, a pair of spray gun mounts on opposite sides of the path of body travel, each mount including a pair of cooperating members,

` means pivoting one of said members for swinging movement about a vertical .axis and means supporting the other member for translatory movement in a direction transverse to the path of body travel, a rocksha'ft having crank arm connections with the swinging'members of both mounts for simultaneously -swinging the same in directions counterrelated, motion transmitting linkage connected with the otherl members of both mounts and arranged to shift the same in unison toward oneanother or away from one another and body driven camming mechanism controlling both of said movements.

2. In a paint spraying machine, a conveyor drive, a body carrying dolly driven by the conveyor drive, a pair of body side wall paint spraying structures located on opposite sides of the path of conveyor travel, each of said structures including a sub-base, means pivotally mounting the sub-base for oscillation about a vertical axis v between limits on opposite sides of a, plane normal to the direction of conveyor travel, a base slidably supported on the sub-base for translatory move porting the base for lateral travel, and means pivotally mounting said sub-base on a vertical 4 axis.

4. Means for spray painting the longitudinally curved wall of a traveling body including a. pair .of interconnected supporting base structures.

means mounting one of said structures for translatory -movement laterallyA of the direction of body travel, means mounting the other structure for swinging about a substantially vertical axis, an upright track carried by said structures to participate in the motions of both thereof and arranged to guide reciprocation of a gun carriage across the body surface, motion cycling mechanism, drive means therefor actuated by body travel and operative connections between'said motion cycling mechanism and the supporting base structures.

5. Means for spray painting the longitudinally curved wall of a traveling body including a pair of upright tracks spaced apart in the longitudinal direction of body travel, an adjustably mounted base structure carrying both tracks for movement relative to the body traveling past the same to maintain desired operative relation to the body surface, a pair of gun carriages guided by the tracks, common drive means to reciprocate said carriages and connections between the drive means and the carriages arranged to reciprocate said carriages in counterbalancing relation.

6. For spray painting the top and side wall curved surfaces of a body traveling a conveyor system, a series of guide tracks for reciprocatory spray guns, arranged one on each side and one across the top of the path of body travel, means supporting each track for rocking and translatory movements needed to maintain operative relation with the body surfaces, a track motion actuator responsive to body travel and operative connections between said -actuator and said tracks, including cycling mechanism driven by said actuator and a track interconnected follower drive engaged with said cycling mechanism.

7. For spray painting the irregular surface of a traveling body, a spray gun guide track extending transversely of the path of bodytravel, a track support mounted for translatory movement toward and from the body travel path and for rocking movement about a transverse axis and in which movements the track participates, said support having oppositely extending lever arms. a pair of vertically shiftable rods connected with said lever arms'to impart relative motion thereto and a pair of rotary cams associated with said rods, respectively, to shift the same in cycle as said cams are rotated. l

8. In a painting machine, frame uprights at each side having vertical g'uideways, a transverse rail having opposite end portions located by said guideways and carrying a pair of oppositely projecting lever arms adjacent each end, means supporting said rail for vertical translatory and rocking adjustments in the guideways, a gun carriage track extending below and parallel to said rail and also having a pair of oppositely projecting lever arms at each end for cooperation with the rail lever arms, a pair of suspension links connecting the rail and track lever arms at each side in parallelogram arrangement for imparting to .the track the path of movement followed by the rail, motion transmitting links joined at their upper ends to the rail lever arms and interrelated camming elements tracking the links, respectively, and thereby controlling rail and TRACY F. BRACKETT.- 

